The Biochemical Function of Cells 



407 



then seen to become slower or stop during the next 45-60 minutes, after which 

 it begins to get faster again though it does not become so fast as it was at first. 

 The optimum pH (8-5) for the incorporation of labelled glycine into the protein 

 of the chloroplasts is different from that (yo) for structures derived from animal 

 sources. Furthermore, the process of incorporation of amino acids into the protein 

 of the structures of animal and plant cells is affected in a different way by the 

 inhibitory factor which we discovered in a supernatant of a homogenate of 

 leaves. It may be hoped that a further comparative study of the biochemical 

 properties of the protoplasmic structures of animal and plant cells will enable 

 us to explain the pecuharities which characterize the qualitatively new laws of 

 metabohsm of the green plant. The differences in the catalytic and functional 

 properties of structures of different origins is closely associated with features of 

 the chemical nature of the protoplasmic structures. Table 2 shows some of the 

 differences in the chemical nature of the protoplasmic structures. 



Table 2 



Chemical composition of the cell units 



(% of dry weight) 



Thus, judging from the figures given in Table 2, there are definite differences 

 in the chemical composition of the fundamental types of structural formation of 

 the plant and animal cells. Such differences, however, are not only found be- 

 tween structures of the same type, of animal and plant origin, but also in one and 

 the same structure, depending on the physiological state of the organism and the 

 type of metabolism. Thus, as may be seen from Table 3, the nucleic acid content 

 changes considerably with changes in the physiological state of the plant. The 

 arrangement of the nucleic acid of the chloroplast by layers, which is character- 

 istic of the stage of bud formation and of the ripening of the seeds, is radically 

 changed during the flowering period of the plant. 



The differences in the chemical composition of the chloroplasts are deter- 

 mined, not merely by the physiological state of the organism, but also by the 

 type of its metabolism. Thus, according to Osipova's findings (see Table 4) 

 [50-52], the contents of proteins, lipids, starch and chlorophyll in the chloro- 

 plasts of the leaves of the broad bean, the sunflower and the potato are signi- 



